BEIRUT — A broad range of estimates has been offered on how many Syrians were killed in the suspected chemical weapons attack near Damascus on Aug. 21 that seems poised to drag the U.S. into Syria’s 2½-year civil war. Here’s a look at who is saying what and on what basis.

United States

The U.S. government says its preliminary figures show 1,429 people were killed, including 426 children, but that this “will certainly evolve” as more information is obtained. Secretary of State John Kerry presented the death toll as part of the administration’s overall intelligence assessment of what happened during the attacks, based on satellite and signal intelligence as well as information from activists, regime sources and social media. Kerry did not say specifically how the death toll was compiled, but cited it as he made the case for punishing the Syrian regime the U.S. blames for the attack.

Syrian opposition

The Syrian National Coalition, the main Western-backed political opposition group, says at least 1,460 people were killed in the strikes on rebel-held western and eastern suburbs of Damascus. The coalition and Majed Abu Ali, who said he is a spokesman for 17 clinics and field hospitals east of Damascus, provided a list of 395 names of people killed. On that list, some of the victims were only identified by their first name or said to be members of a certain family.

Abu Ali said the overall death toll is based on reports received from the clinics, but would not elaborate or provide a breakdown of the number of dead counted at each clinic. He said the total could be off slightly due to possible double-counting as victims were being moved. Three other senior anti-regime activists referred questions to Abu Ali.

Doctors with Borders

The humanitarian aid group says it has not been able to update its initial Aug. 24 estimate of 355 killed because communication with people on the ground in the Damascus area is difficult. That estimate was based on reports by doctors in three clinics in the Damascus area that are supported by the group.

Doctors Without Borders does not have a list of the names of the dead and won’t say from which three hospitals the data came, citing security reasons.

Human Rights Watch

The New York-based group received reports from doctors and activists from clinics in four Damascus suburbs — three in the east and one on the west — on the day of the attack. Based on these reports, the group says the death toll is “at least in the hundreds,” but that it is unable to give an exact figure.

United Nations

U.N. spokesman Martin Nesirky has said he does not know if the U.N. chemical weapons experts who visited stricken areas earlier this week would provide a death toll as part of their investigation of the Aug. 21 attacks.